Sergio Aguero's late goal helped Atletico Madrid come from behind to beat Barcelona 4-3 and blow the Spanish title race wide open.
Barcelona, who led 2-0 and 3-2 on Sunday, have now failed to win in four matches and have seen their lead over Real Madrid cut from 12 points, just three weeks ago, to four.
Thierry Henry put Barcelona ahead with a fine strike from 25 yards which flew into the top corner after 18 minutes before Lionel Messi, on the half-hour mark, produced a trademark dribble before finishing in style.
Diego Forlan brought Atletico back into the match with a spectacular 30-yard drive before Aguero got the first of his brace after 56 minutes.
Barcelona, who were stunned by struggling Espanyol last weekend, re-established their lead when Eidur Gudjohnsen unselfishly played in Henry for his second from close range in the 73rd minute.
But Atletico were not finished and Forlan again scored, this time from the penalty spot in the 80th minute, before Aguero struck in the 89th minute to win the match.
Meanwhile, the pressure is growing on Valencia coach Unai Emery as his side followed their mid-week UEFA Cup elimination with a 2-1 home defeat by Valladolid.